Method of recording and reproducing information

ABSTRACT

A heat-sensitive recording material of the type covered by U.S. Pat. No. 3,476,937 and including a recording layer formed of a dispersion of solid hydrophobic thermoplastic polymer particles in a water-soluble hydrophilic binder is modified to include a diffusion-resistant colorant material and a visible finely divided material absorbing radiation and converting the same into heat, such material being either chemically bleachable or soluble in an aqueous liquid. The resultant heat-sensitive material is exposed to radiation pattern and then contacted with at least one liquid to bleach or dissolve the radiation absorbing and converting material and to remove by washing the water-soluble portions of the recording layer, the portions corresponding to the radiation pattern having been rendered water-insoluble by the exposure step but remain water-permeable to permit the radiation absorbing and converting material to be bleached or dissolved by penetration of the liquid.

United States Patent Vrancken et al.

[4 Feb. 15, 1972 [54] METHOD OF RECORDING AND REPRODUCING INFORMATION[72] Inventors: Marcel Nicolas Vrancken, Hove; Daniel [30] ForeignApplication Priority Data Oct. 2, 1967 Great Britain ..44,765/67 [52]US. Cl. ..96/35, 96/60 R, 96/ 1 14.1, 117/63, 250/65 T [51] Int. Cl..G03l 7/10, G03c 5/00 [58] Field ofSearch ..96/27,60,114.1, 35;250/651; 117/361, 36.2, 63; 101/467, 470

[56] References Cited UNITED STATES PATENTS 2,629,671 2/1953 Murray..117/8 2,936,247 5/1960 Francis et al... .117/36.1 3,121,162 2/1964Roman et al. ....250/65 3,223,838 12/1965 l-loshino et al.. ....250/653,298,833 1/1967 Gaynor ..250/65 3,405,265 10/1968 Vrancken ..250/653,476,578 11/1969 Brinckman..... .250/65X 3,476,937 11/1969 Vrancken..250/65 Primary Examiner-William D. Martin Assistant ExaminerEdward J.Cabic Attorney-William J. Daniel [57] ABSTRACT A heat-sensitiverecording material of the type covered by US. Pat. No. 3,476,937 andincluding a recording layer 1 formed of a dispersion of solidhydrophobic thermoplastic polymer particles in a water-solublehydrophilic binder is modified to include a diffusion-resistant colorantmaterial and a visible finely divided material absorbing radiation andconverting the same into heat, such material being either chemi- Callybleachable or soluble in an aqueous liquid. The resultant heat-sensitivematerial is exposed to radiation pattern and then contacted with atleast one liquid to bleach or dissolve the radiation absorbing andconverting material and to remove by washing the water-soluble portionsof the recording layer, the portions corresponding to the radiationpattern having been rendered water-insoluble by the exposure step butremain water-permeable to permit the radiation absorbing and convertingmaterial to be bleached or dissolved by penetration of the liquid.

1 1 Claims, No Drawings M ETHOD'OF RECORDING AND. REPRODUCINGINFORMATION The present invention relates tomethods for recording andreproducing information and to materials for use in said methods. Theinvention more particularly but not exclusively relates to a method forrecording imagewise or recordwise modulated light energy, which istransformed into heat in a heatsensitive recording material.

It has been proposed to record information by informationwise heating arecording, layer composed so that under the action of such heating itundergoes a change in water-permeability. In consequence of theinformationwise heating the information is therefore recorded in termsof a difference in the water-permeabilities of different areas of therecording layer.

Certain recording materials for use in that way, and recording processesusing such materials, are described and claimed, inter alia, in BelgianPat. specification No. 656,713 and in the published Dutch Pat.application No. 6,606,719 corresponding to US. Pat. No. 3,476,937. Suchrecording materials have recording layers comprising a network ofhydrophobic thermoplastic polymer particles, solid, at room temperature,or comprising hydrophobic thermoplastic polymer particles dispersed in acontinuous phase hydrophilic binder medium.

Other recording materials in which information can be recorded in termsof a differential water-permeability by informationwise heating arecording layer are described and claimed in Belgian Pat. specificationNos. 682,767 and 683.054. In such recording materials the recordinglayer is composed wholly or mainly of gelatin which becomes morewater-soluble and consequently more water-permeable, when sufficientlyheated.

An interesting development of this principle of recording information isthe use of a recording material which contains one or more distributedsubstances capable of absorbing electromagnetic radiation, e.g.,infrared radiation and/or visible light, and in which the recordinglayer becomes heated by virtue of radiation absorption by suchsubstance(s) when the recording material is irradiated. The aforesaidearlier patent specifications include descriptions of recordingmaterials useful in that way, and further such materials are describedin Belgian Pat. specification No. 681,138. When a radiation-absorbingsubstance is distributed in the recording layer, the informationwiseheating of the recording layer which brings about the water-permeabilityor water-solubility differentiation can be achieved by informationwiseexposing the recording material to sufficient radiation of theappropriate type.

The presence of the radiation-absorbing substance(s) in the aforesaidrecording materials makes the record visible, provided the recordingmaterial is treated, following the informationwise heating, to removethe recording layer selectively in dependence on the water-permeabilitypattern. It will be apparent however that the result of forming avisible record in that way is that the color and optical density of therecord is determined by the substance(s) used for absorbing theelectromagnetic radiation. It is also possible, following theinformationwise heating of the layer to allow a colored substance topenetrate differentially into the layer according to thewater-permeability pattern, but the still present radiation absorbingsubstance(s) impair the color and contrast of the developed record.

The present invention provides an improved process, according to whichradiation-absorbing substance(s) used for heat generation in therecording layer is or are entirely or substantially entirely removedfrom the recording layer after a record in terms of a water-permeabilitydifferentiation has been formed.

The present invention includes any information recording process whereina recording layer which is composed so that it undergoes a change ofwater-permeability under the action of heat and which contains asubstance or substances which can absorb certain electromagneticradiation, is informationwise heated by irradiation of such layer withelectromagnetic radiation which is absorbed by said substance(s) so thatsaid information is recorded in terms of a difference in thewaterpermeabilities of difierent areas of such layer, and the saidradiation-absorbing substance(s) is or are then bleached in or leachedout of said layer without destroying the waterpermeabilitydifferentiation.

The invention also includes, by way of modification, anyinformation-recording process as abovedefined but wherein following theinformationwise heating which establishes the record in terms of awater-permeability differentiation, selected parts of the recordinglayer are removed depending on their water-permeability, and theradiation-absorbing substance(s) in the remaining portions of the layeris or are bleached in or leached out from such remaining portions.

The composition of the recording layer may be such that after thebleaching or leaching operation the recording layer is substantiallycolorless. The latent record can be subsequently developed by allowing acolored developer, e.g., a dye solution, to penetrate into the layer orthe remaining portions thereof. Obviously a wide choice of developer isavailable since the only function of the developer is to provide therequired color in the developed record. i

According to preferred embodiments however the recording layer initiallycontains not only the necessary radiation-absorbing substance(s) butalso a colored ingredient or ingredients providing the final recordcolor or colors, the nature of such ingredient(s) being such that theradiation-absorbing substance(s) can be bleached in or leached out ofthe recording layer without affecting the said colored ingredient(s).

The present invention also includes any recording material having arecording layer which is composed so that it undergoes a change ofwater-permeability under the action of heat and which contains (a) atleast one distributed substance capable of absorbing certainelectromagnetic radiation and thereby-yielding heat to bring about asaid change in waterpermeability, and (b) at least one coloringingredient or colorformer of such nature that it can remain in the layersubstantially unaffected if the latter is treated with an appropriatelyselected liquid composition which bleaches or leaches saidradiation-absorbing substance in or from the layer. The expression colorformer includes a mixture of components capable of entering into acolor-forming reaction in the layer when heated or subjected to otherconditions.

Heat-sensitive recording materials useful in carrying out the presentinvention include materials containing a hydrophilic colloid and whichin itself or by the action of substances dispersed or dissolved thereinbecome less water-permeable, as described e.g., in the Belgian Pat.specification Nos. 656,713, 676,329, 674,218, 681,138, 683,053 and705,529 and in the published Dutch Pat. application No. 6,705,963.

Other heat-sensitive recording materials useful in carrying out thepresent invention include materials containing a hydrophilic colloid,more particularly gelatin and preferably gelatin of the type describedin the United Kingdom Pat. specification No. 985,933, which by theaction of heat becomes more water-soluble and consequently morewaterpermeable, as described in the Belgian Pat. specification No.682,767.

According to a preferred embodiment a recording material is usedcomprising at least one heat-sensitive layer undergoing a decrease inpermeability to water when heated, and incorporating particles composedwholly or mainly of a hydrophobic thermoplastic polymer. Said layercontains preferably a major part by volume of a dispersion of saidparticles in a hydrophilic binder in a weight ratio greater than 1:1 aswell as an amount of a colored substance which absorbs infraredradiation and/or visible light and converts a substantial partPreferably, the heat-sensitive layer used in the present invention, atroom temperature incorporates solid particles of hydrophobicthermoplastic polymeric material, which has been dispersed in an aqueousmedium by means of a dispersing agent. The sensitivity of the recordinglayers depends on the concentration of the said thermoplastichydrophobic polymer particles in the hydrophilic binder and preferredcompositions contain these particles in a weight ratio of at least 3:2.The said recording layer for reason of sensitivity preferably consistsfor at least 50 percent by volume of the dispersion of said hydrophobicpolymer particles in the h ydrophilic binder. As a matter of course thesensitivity of the recording layer also depends on the concentration ofthe lightabsorbing heat-generating substance(s) and its (their)absorption spectrum. Preference is given to dark substances, whichabsorb electromagnetic radiation in a visible part of theelectromagnetic spectrum as large as possible, and preferably in theinfrared region (wavelength beyond 700 nm.). If the recording materialis to be used in a reflex exposure, the concentration of heat-generatingsubstances should be such that the optical density to applying lightpreferably is comprised between 0.2 and 0.8. Recording materialsappliedin direct exposure preferably possess an optical density of at least 1.The sensitivity of the preferred heat-sensitive layers is such that anexposure energy of only 0.3 watt.sec./sqcm. is required for producing apractical useful differentiation in water-permeability.

The light-absorbing substances wherein by exposure to visible and/orinfrared light heat is generated are preferably bleachable substancese.g., bleachable metals or dyes or dyes of the water-soluble type, e.g.,dyestuff salts, or are easily soluble in aqueous compositions containinga certain amount of a water-miscible organic solvent, e.g., ethanol, anacid which improves the removal of basic dyestuffs, or a base which canimprove the removal of acid dyes.

Light-absorbing heat-generating substances which are suited to be usedaccording to the present invention are preferably colored ionicsubstances with a high rate of diffusion in gelatin coatings swollen inwater. The measurement of dye diffusion rates in swollen gelatincoatings has been described by R. B. Pontius and I. A. Wenrich in Phot.Sci. and Eng, Vol. 2, No. 3, Oct. 1958, p. 131-135. Preferably anionicor cationic nondiffusion resistant organic dyes containingwater-solubilizing salt or acid groups are used, e.g., acid orneutralized acid dyes used in the hydrotype printing process for theproduction ofimbibition prints. Examples of such dyes can be found inthe U.S. Pat. specification No. 2,892,822. It is to be understood thatmixtures ofsuch dyes can be used too.

In the recording, preference is given to a short-duration high-intensityimagewise exposure. An advantage of this type of exposure is that ityields a reproduction with great image sharpness, since the lateraldiffusion of heat is limited here to a minimum value. Thus, it ipreferred in carrying out the exposure step to apply an imagewise orinformationwise exposure lasting no longer than 10 sec. The exposuremust be sufficiently intense in order to effect the desired decrease inwaterpermeability in the exposed areas.

Suitable radiation sources for producing copying light of high intensityin a rather short period of time are so-called flash-lamps. Good resultsare obtained with xenon gas discharge lamps with an exposure time of lto These flash lamps emit a larger part of visible light than ofinfrared V radiation. Details on a copying device containing such adischarge lamp can be found in the Belgian Patent Specification 664,868and in the published Dutch Pat. application No. 6,808,648.

If the emitted energy is focused onto a relatively small heatsensitivearea, e.g., of the size of one picture of a motion picture film a gasdischarge lamp with a relatively low energy output can be used. E.g.,for copying on an area of 19 mm. X 35 mm. a flash lamp with an energyoutput of 40 watt.sec. will suffice.

Self-evidently, the heat-sensitive surface layer before or during theimagewise exposure to heat-generating radiation can be subjected to anoverall heating to a certain temperature below the temperature at whicha substantial decrease in permeability to water takes place. In thisway, less imagewise supplied heat-generating electromagnetic radiationis required to produce the desired reduction in water-permeability.

The technique of the integral removal by bleaching or leaching out ofcolored heat-generating substances from the heat-exposed recording layeropens up the possibility to produce colored or black prints withouthaving to selectively remove the nonheated portions of the recordinglayer.

According to a particular embodiment the light absorbing heat generatingsubstances are integrally removed after the imagewise light exposure andrelying on the difference in water-permeability between the exposed andnonexposed portions of the recording layer a positive color print iobtained by differential penetration of a dye solution. The density ofthe color print is directly proportional to the degree ofwaterpermeability of the nonheated portions of the recording layer. Thedisturbing effect of a dark image background which would have beenpresent if the heat-generating substances had not been removed iscompletely excluded here.

In this connection reference is made to the published Dutch Pat.application No. 6,806,658, wherein the production of positive images byimagewise water-permeability differentiation is described. According toan embodiment of the invention described therein the heat-sensitivelayer containing light absorbing pigments has to be removed integrallyfrom an image containing layer. The present method is especiallyinteresting in such a case wherein it is interesting to maintain theheat-sensitive layer on top of the image containing layer avoidingdamaging of the underlying layer.

According to an important embodiment pigments that are fast to light,e.g., yellow, cyan or magenta diffusion-resistant pigment dyes, areincorporated into the heat-sensitive layer together with thelight-absorbing and heat-generating substances which can be washed away.After imagewise exposure the heat-generating substances are integrallyleached out, e.g., by means of tap water, and the heat-sensitive layeris washed away in accordance with the nonexposed areas, so that aspectrally pure pigment dye image of high fastness to light is left. Byapplying the latter embodiment of the present invention it is possibleto obtain yellow dye images by heat-generating exposure e.g., infraredexposure and subsequent selective removal of the recording layer bywashing away. In order to understand the advantage associated with saidtechnique, it has to be noted that by means of yellow dyes as the solelightabsorbing colored component in the heat-sensitive layer this waspractically impossible so far, as yellow dyes absorb only a minor partof the visible light and none of infrared light so that by exposurelittle or no heat is generated in said dyes.

The use of removable heat-generating substances thus makes it possibleaccording to the present invention to record an image of any color in aphotothermographic way of combining said removable heat-generating dyeswith one or more colored substances which are fast to diffusion, e.g.,pigments conferring the desired color to the image.

By means of this technique it is possible to produce color images forcolor proofing. Color-proofing materials serve to form a proof forsubmission to the printer to give an idea of a multicolor reproductionas will be produced by imagewise overprinting with four inks (yellow,magenta, cyan and black) printed at the strength normally used inpractice. The proof obtained wit a color proofing material enables todetermine the necessary corrections of the intermediate negatives usedin preparing the etching resists and to adapt the exposure conditions.In an already existing method for preparinglsuch a colorproof use ismade of a multicolor silver halide'photographic material which isexposed through the screened blackand-white selection negativescorresponding respectively with the yellow, magenta, cyan and blackseparation images of a multicolor original. The difficulty associatedwith said method resides in finding the right color couplers for formingdyes having an absorption spectrum practically identical t that of theprinting dyes or pigments used. The method of the present inventionprovides a solution of that problem in that previously prepareddyestuffs or pigments with the right absorption spectrum can be appliedin nonmigratory state.

According to one technique a multicolor proof is obtained bysuccessively coating, exposing and developing four heatsensitivehydrophilic water-permeability differentiable layers which contain ablack, a cyan, a magenta and a yellow pigment dye respectively throughthe corresponding black-andwhite selection negatives of the multicolororiginal to be reproduced by printing. The said heat-sensitive layersare separately coated on one and the same support. Following itscoating, each of the four heat-sensitive layers is exposed to lightthrough the proper black-and-white selection negative, and thedevelopment carried out by washing away the nonexposed portions of theexposed recording layer removing at the same time the nondiffusionresistant light-absorbing heatgenerating dyes in the exposed portions.

According to another technique the pigment coatings are applied to fourseparate transparent supports. After exposure and processing the imageswere brought in register and examined by means of transmitted light,e.g., in a diascope, or overhead projector.

According to said techniques the colored heat-sensitive layers containin addition to dark heat-generating bleachable or removable substances,a dye, a pigment or a mixture of both, which resists diffusion and whichdye or pigment has an absorption spectrum as conform as possible to thatof the color of the printing dye for each printing step (cyan, magenta,yellow).

As is known the magenta ink pigments have unwanted absorptions in theblue region of the spectrum, and to a much less extent in the red one,the magenta ink prints as if it were a true magenta ink containing someyellow and a little cyan. Normally sufficient correction is obtained byreducing the amount of yellow in proportion t the amount of magentaprinted.

The cyan ink pigments have unwanted absorptions in the blue and greenregions of the spectrum; the cyan ink prints as if it were a true cyanink containing magenta and yellow.

The yellow ink pigments normally approaches the ideal way of absorbingblue light and no correction is necessary unless it is a specialwarm-ink (orange-yellow) in which case it may be desirable to reduce thestrength of the magenta printed in the yellow areas.

The black toner being preferably present in the first exposed layer canbe a black or grey pigment, e.g., carbon black or dark metal particles,their sulphides and oxides, e.g., nickel, lead, silver, bismuth,lead(lV) oxide, copperfll) oxide and copper(ll) sulphide. Theblack-toned material preferably contains carbon black in theheat-sensitive layer, which preferably is applied to a subbing orinterlayer of the type described in the Belgian Pat. specification No.692,422.

Nonmigratory pigments suitable for use in the color proofing system ofthe invention are known under the trade name Pigmosol dyes. Pigmosol isa registered trademark of Badische Anilin- & Soda-Fabrik A.G.,Ludwigshafen/Rh., W.-Germany, for organic pigment dyes which are mixedwith a dispersing agent for aqueous medium. These pigment dyes are veryresistant to light, heat, acids and bases. They are insoluble inhydrophilic colloids, e.g., gelatin and poly-N-vinylpyrrolidone whichcolloids are preferably used in heat-sensitive layers intended for usein the washing away technique.

The following examples illustrate the present invention.

EXAMPLE 1 A polyethylene terephthalate support of 0.1 mm. thickness wascoated with thefollowing composition pro rata of 17 g. per sq.m.:

20% aqueous dispersion of copoly (vinyIidcne-chloride/N-butylmaleimide/itaconic acid) (88Il0/2) with an average particle size of 0.1 40 g.

40% aqueous dispersion of polyethylene having a particle size of lessthan 0.1;4 and an average molecular weight comprises between 15,000 and30,000 40 g.

30% aqueous dispersion of silica with an average particle size of 002540 ml.

water 780 ml.

ethanol ml.

10% aqueous solution of poly-N- vinyl pyrrolidone ml.

40% aqueous dispersion of polyethylene as described above g.

water 120 ml.

aqueous carbon dispersion containing per 100 g. 16 g. of carbon (averageparticle size 0.1 and 2 g. of poly-N-vinyl pyrrolidone 450 ml.

3% aqueous dispersion of the sodium salt of tetradecyl sulphate 65 ml.

The heat-sensitive layer was dried at 30 C. While in contact with ablack-and-white selection negative corresponding with those parts of anoriginal that had to be printed in black, the heat-sensitive materialwas exposed for 1/2000 sec. through said selection negative by means ofa xenon gas discharge lamp of 1,000 watt.sec. Subsequently, theunexposed portions of the recording layer were washed away with water sothat a positive image was obtained in accordance with those parts of theoriginal that have to be printed in black.

The layer comprising the black image was then coated with a secondthermosensitive layer comprising a cyan pigment for the formation of thecyan image areas. The black image layer was therefor mountedhorizontally in a centrifuge rotating at 100 revolutions per min. at atemperature of 43 C. The following composition was poured onto the blackimage layer to form a coating which, on drying comprises 30 g. per sq.m.

40% aqueous dispersion of polyethylene as described above 100 g. 20%aqueous dispersion of poly-N-vinyl pyrrolidone 20 ml.

10% aqueous solution of a compound corresponding to the followingstructural formula:

, 7% aqueous solution ot'a compound OgNa lIrN- -@-c on,

I S 03 =N z S OrNa 100 ml.

3% aqueous solution of sodium tetradecylsulphatc 20 ml.

After having been dried the material obtained was exposed, while inregister contact with a black-and-white selection negative correspondingwith those parts of the original that had to be printed in cyan, theexposure being effected through the said selection negative by means ofa xenon gas discharge lamp of 1,000 watt.sec. for l/2000 sec.

Subsequently the unexposed portions of the recording layer were washedaway with water, the water-soluble dyes in the exposed areas beingrinsed away immediately. The black image already present remainedintact. The image obtained consisted of black and cyan parts. Thematerial was then coated again with a thermosensitive layer comprising ayellow pigment for the formation of a yellow image. The composition wasanalogous to that of the preceding thermosensitive layer, but instead of22 g. of Heliogen Blau B Colanyl Teig use was made of g. of PermanentGelb HR Colanyl Teig (a yellow pigment insoluble in water, sold byFarbwerke H6chst A.G. Frankfurt(M) Hdchst, W.-Germany).

The resulting material was then exposed through a blackand-whitenegative corresponding with those parts of the original that had to beprinted in yellow.

After having been washed the material was coated again with acomposition analogous to that of the preceding layer, with theexception, however, that g. of Permanentcarmin FBB Colanyl Teig (amagenta pigment insoluble in water, sold by Farbwerke Hochst A.G.Frankfurt(M) Hiichst, W-Germany) was used therein instead of the 22 g.of Heliogen Blau B Colanyl Teig.

After having been dried the resulting material was exposed now through ablack-and-white selection negative corresponding with those parts of theoriginal that had to be printed in magenta.

Thus, a four-color image suitable for color proofing was obtained. Bymeans of this four-color image the quality of the selection negativesand the future print wasjudged of easily.

EXAMPLE 2 A polyethylene terephthalate support having a thickness of0.075 mm. was coated with a subbing layer as described in Example l. Thesubbing layer itself was coated pro rata of 18 g./sq.m. with a blackheat-sensitive layer comprising:

an aqueous dispersion of polyethylene comprising per [00 g. 18 g. ofpoly ethylene (the polyethylene dispersion was prepared by dispersingpolyethylene in water at I60 C.) with 2.5 g. of nonylphenylpoly(ethyleneoxyde)n (the average value of n==9 l0), 2.5 g. ofnonylphenylpoly(ethyleneoxyde),,, ethanol (the average value of m=7) and0.4 g. of

potassium hydroxide 175 ml.

water 465 ml.

an aqueous cnrhon dispersion comprising er I00 g. lo g. ofcarhonparticles hanng il sue oft In and I g. of polyl'\'-\in \l p \\r\ litiune400 ml.

3? aqueous solution of sodium tetradectl sulphate 50 ml.

l0; aqueous solution of animal glue I20 ml.

After having been dried the resulting material was exposed as describedin Example I, while in contact with a black-andwhite selection negativecorresponding with those parts of the original that had to be printed inblack. The further treatments were analogous to those described inExample 1, with the proviso, however, that the following threedifferently colored heat-sensitive layers were coated successively prorata of 40 g./sq.m.:

l. A thermosensitive layer comprising a cyan pigment:

aqueous dispersion of polyethylene comprising l8% of polyethyleneprepared as described above 200 ml.

water 300 ml.

20% aqueous dispersion of poly-N-vinyl pyrrolidone 20 ml.

Heliogen blau B Colanyl Teig (see Example I) 50 g.

5% aqueous solution of a diffusible dye corresponding to the structuralformula:

7% aqueous solution ofa diffusible dye corresponding to the structuralformula:

? OzNa H N C CH;

| S 0 =NH S O Na 125 ml.

ethanol 76 ml,

2. A thermosensitive layer comprising a yellow pigment, the compositionof the layer being analogous to that of the preceding one, wit theproviso, however, that the 50 g. of Heliogen blau B Colanyl Teig werereplaced by g. of Paliogengelb RT Colanyl Teig (a pigment paste) sold byBadische Anilin- & Soda-Fabrik A.G. Ludwigshafen/Rh., W- Germany).

3. A thermosensitive layer comprising a magenta pigment, said layerhaving a composition analogous to that of the preceding one, but whereinthe 50 g. of Heliogen Blau B Colanyl Teig were replaced by 100 g. ofHelioechtrot ITR Feinteig (a pigment dispersion sold by FarbenfabrikenBayer A.G., Leverkusen, W.-Germany).

EXAMPLE 3 A heat-sensitive material consisting of a polyethyleneterephthalate support, a subbing layer, and a black heat-sensitive layeras described in Example 1, was exposed through a selection negativewhile in contact therewith, said selection negative corresponding withthose parts of the original that had to be printed in black, and theexposure being effected with the aid of a xenon gas discharge lamp of1,000 watt.sec. in 2/1000 sec. After washing away of the unexposed areaswith water, the material mounted horizontally in a centrifuge rotatingat 100 revolutions per min. was coated therein at a temperature of 45 C.pro rata of 40 g./sq.m. with a composition comprising the followingingredients:

40% aqueous dispersion of polyethylene (see Example I) 100 ml.

water 200 ml.

Heliogen blau B Colanyl Teig (see Example I) 25 g.

20% aqueous dispersion of poly-N- vinyl pyrroliclone 20 ml.

l% aqueous dispersion of black silver particles 400 ml.

3% aqueous solution of sodium tetradecyl sulphate 20 ml.

After having been dried the material was exposed through ablack-and-white selection negative corresponding with those parts of anoriginal that had to be printed in cyan, the selection negative beingbrought in register contact with said material. After washing away ofthe unexposed portions of the recording layer, the material was coatedagain with a composition analogous to that of the preceding layer, withthe proviso, however, that the 25 g. of Heliogen Blau B Colanyl Teigwere replaced by g. of Permanent Gelb HR Colanyl Teig sold by Hiichst.

The resulting material was exposed through a black-andwhite selectionnegative corresponding with those parts of the original that had to beprinted in yellow. After washing away of the unexposed areas, thematerial was again coated with a solution analogous to the firstdescribed, with the exception, however, that the 25g. of Heliogen Blau BColanyl Teig were replaced by g. of Permanentcarmin FBB Colanyl Teig(see Example 1).

After exposure through a black-and-white selection negativecorresponding with those parts of the original that had to be printed inmagenta and after washing away the nonexposed portions the material wasimmersed for 60 sec. in a common bleaching bath (Farmers reducer),whereby the black residual silver in the three-color layer material wasbleached away. The material was then rinsed and dried. A three-colortransparency was obtained finally. The said transparency was used in aprojection technique known as overhead projection.

We claim:

1. A method of reproducing information comprising exposing to anelectromagnetic radiation pattern according to said information aheat-sensitive recording material including a water-permeable recordinglayer formed by a dispersion of hydrophobic thermoplastic polymerparticles in a continuous phase of a water-soluble hydrophilic binder ina ratio by weight of at least 121, said hydrophilic binder continuousphase also having distributed therethrough a water-insoluble colorantmaterial resistant to diffusion from said continuous phase and awatersoluble visible finely divided material absorhing radiation andconverting the same into heat, said recording layer after said exposurebeing water-insoluble but permeable to aqueous liquids, and after saidexposure contacting said exposed recording layer with at least oneaqueous liquid to dissolve said water-soluble radiation absorbing andconverting material and to remove by washing the water-soluble portionsof said layer, whereby the remaining portions form a colored reliefimage corresponding to said radiation pattern.

2. A method of reproducing information according to claim 1, wherein thedispersion consisting of hydrophobic polymer particles in thehydrophilic binder medium i present in the recording layer for at least50 percent by volume.

A method of reproducing information according to claim 1, wherein thehydrophobic polymer particles are latex particles solid at roomtemperature and are present in said continuous hydrophilic binder mediumin an amount by weight of at least 3:2.

4. A method of reproducing information according to claim 1, whereinsaid water-soluble colorant material is a diffusible anionic or cationicorganic dye containing water-solubilizing salt or acid groups.

5. A method of reproducing information according to claim 1, wherein theexposure is a short-duration high-intensity imagewise exposure.

6. A method of reproducing information according to claim 5, wherein theexposure lasts no longer than 10' sec.

7. A method of producing information as a multicolor print according toclaim 1, wherein said recording material includes four of saidheat-sensitive recording layers applied thereon separately, said layersrespectively contain a black, a cyan, a magenta, a yellow pigment, eachlayer containing a watersoluble dark colored substance which absorbs atleast a part of the copying light and transforms it into heat and eachlayer is separately exposed in turn to light through a properblackand-white screened selection negative of the color original to bereproduced and each layer following its exposure and before applicationto the next layer is treated with an aqueous liquid to remove thenonexposed portions and dissolve out the dark colored substance.

8. The process of claim 1 wherein the same aqueous liquid serves todissolve said water-soluble radiation absorbing and converting materialand to remove said water-soluble portions of said layer.

9. The process of claim 1 wherein the water-soluble portions of saidexposed recording layer are first washed away with water and saidwater-soluble radiation absorbing and converting material in theremaining water-insoluble portions of said layer is then dissolved bycontact with an aqueous solution.

10. The process of claim 1 wherein said colorant material is adiffusion-resistant colored or black pigment or dye.

11. A method of reproducing information comprising exposing to anelectromagnetic radiation pattern according to said information aheat-sensitive recording material including a water-permeable recordinglayer formed by a dispersion of hydrophobic thermoplastic polymerparticles in a continuous phase of a water-soluble hydrophilic binder ina ratio by weight of at least 1:], said hydrophilic binder continuousphase also having distributed therethrough a colorant material resistantto diffusion from said continuous phase and a finely divided particlesof visible silver metal absorbing said radiation and converting the sameinto heat, said recording layer after said exposure beingwater-insoluble but permeable to aqueous liquids, and after saidexposure contacting said exposed recording layer with an bleachingsolution for said silver converting the same to a water-soluble form andwith a liquid to remove by washing the water-soluble portions of saidlayer, whereby the remaining portions form a colored relief imagecorresponding to said radiation pattern.

2. A method of reproducing information according to claim 1, wherein thedispersion consisting of hydrophobic polymer particles in thehydrophilic binder medium i present in the recording layer for at least50 percent by volume.
 3. A method of reproducing information accordingto claim 1, wherein the hydrophobic polymer particles are latexparticles solid at room temperature and are present in said continuoushydrophilic binder medium in an amount by weight of at least 3:2.
 4. Amethod of reproducing information according to claim 1, wherein saidwater-soluble colorant material is a diffusible anionic or cationicorganic dye containing water-solubilizing salt or acid groups.
 5. Amethod of reprodUcing information according to claim 1, wherein theexposure is a short-duration high-intensity imagewise exposure.
 6. Amethod of reproducing information according to claim 5, wherein theexposure lasts no longer than 10 1 sec.
 7. A method of producinginformation as a multicolor print according to claim 1, wherein saidrecording material includes four of said heat-sensitive recording layersapplied thereon separately, said layers respectively contain a black, acyan, a magenta, a yellow pigment, each layer containing a water-solubledark colored substance which absorbs at least a part of the copyinglight and transforms it into heat and each layer is separately exposedin turn to light through a proper black-and-white screened selectionnegative of the color original to be reproduced and each layer followingits exposure and before application to the next layer is treated with anaqueous liquid to remove the nonexposed portions and dissolve out thedark colored substance.
 8. The process of claim 1 wherein the sameaqueous liquid serves to dissolve said water-soluble radiation absorbingand converting material and to remove said water-soluble portions ofsaid layer.
 9. The process of claim 1 wherein the water-soluble portionsof said exposed recording layer are first washed away with water andsaid water-soluble radiation absorbing and converting material in theremaining water-insoluble portions of said layer is then dissolved bycontact with an aqueous solution.
 10. The process of claim 1 whereinsaid colorant material is a diffusion-resistant colored or black pigmentor dye.
 11. A method of reproducing information comprising exposing toan electromagnetic radiation pattern according to said information aheat-sensitive recording material including a water-permeable recordinglayer formed by a dispersion of hydrophobic thermoplastic polymerparticles in a continuous phase of a water-soluble hydrophilic binder ina ratio by weight of at least 1:1, said hydrophilic binder continuousphase also having distributed therethrough a colorant material resistantto diffusion from said continuous phase and a finely divided particlesof visible silver metal absorbing said radiation and converting the sameinto heat, said recording layer after said exposure beingwater-insoluble but permeable to aqueous liquids, and after saidexposure contacting said exposed recording layer with an bleachingsolution for said silver converting the same to a water-soluble form andwith a liquid to remove by washing the water-soluble portions of saidlayer, whereby the remaining portions form a colored relief imagecorresponding to said radiation pattern.